The threshold wavelength for photoelectric emission from a material is 5200 Å. Photo-electrons will be emitted when this material is illuminated with monochromatic radiation from :

(1) 50-watt infrared lamp

(2) 50-watt ultraviolet lamp

(3) 1-watt ultraviolet lamp

(4) Both (2) and (3)

Threshold frequency for a metal is ${10}^{15}$ Hz. Light of $\mathrm{\lambda }=4000$$\stackrel{0}{\mathrm{A}}$ falls on its surface. Which of the following statements is correct

(1) No photoelectric emission takes place

(2) Photo-electrons come out with zero speed

(3) Photo-electrons come out with ${10}^3$ m/sec speed

(4) Photo-electrons come out with ${10}^5$ m/sec speed

Einstein got Nobel prize on which of the following works

(1) Mass-energy relation

(2) Special theory of relativity

(3) Photoelectric equation

(4) (a) and (b) both

The photo-electrons emitted from a surface of sodium metal are such that 

(1) They all are of the same frequency

(2) They have the same kinetic energy

(3) They have the same de Broglie wavelength

(4) They have their speeds varying from zero to a certain maximum

A metal surface of work function \(1.07\) eV is irradiated with light of wavelength \(332\) nm. The retarding potential required to stop the escape of photo-electrons is:
1. \(4.81\) eV
2. \(3.74\) eV
3. \(2.66\) eV
4. \(1.07\) eV
 

In a photo cell, the photo-electrons emission takes place
(1) After ${10}^{-1}$ sec on incident of light rays

(2) After ${10}^{-3}$ sec on incident of light rays

(3) After ${10}^{-6}$ sec on incident of light rays

(4) After ${10}^{-8}$ sec on incident of light rays

When light falls on a metal surface, the maximum kinetic energy of the emitted photo-electrons depends upon

(1) The time for which light falls on the metal

(2) Frequency of the incident light

(3) Intensity of the incident light

(4) Velocity of the incident light

The electrons are emitted in the photoelectric effect from a metal surface 

(1) Only if the frequency of the incident radiation is above a certain threshold value

(2) Only if the temperature of the surface is high

(3) At a rate that is independent of the nature of the metal

(4) With a maximum velocity proportional to the frequency of the incident radiation

The work function of a metal is \(4.2 ~\text{eV}\), its threshold wavelength will be:
1. \(4000~\mathring{\text{A}}\)                   
2. \(3500~\mathring{\text{A}}\)
3. \(2955~\mathring{\text{A}}\) 
4. \(2500~\mathring{\text{A}}\)

The number of photo-electrons emitted per second from a metal surface increases when: